High-performance, polymer-based direct cellular interfaces for electrical stimulation and recording

Due to the trade-off between their electrical/electrochemical performance and underwater stability, realizing polymer-based, high-performance direct cellular interfaces for electrical stimulation and recording has been very challenging. Herein, we developed transparent and conductive direct cellular interfaces based on a water-stable, high-performance poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film via solvent-assisted crystallization. The crystallized PEDOT:PSS on a polyethylene terephthalate (PET) substrate exhibited excellent electrical/electrochemical/optical characteristics, long-term underwater stability without film dissolution/delamination, and good viability for primarily cultured cardiomyocytes and neurons over several weeks. Furthermore, the highly crystallized, nanofibrillar PEDOT:PSS networks enabled dramatically enlarged surface areas and electrochemical activities, which were successfully employed to modulate cardiomyocyte beating via direct electrical stimulation. Finally, the high-performance PEDOT:PSS layer was seamlessly incorporated into transparent microelectrode arrays for efficient, real-time recording of cardiomyocyte action potentials with a high signal fidelity. All these results demonstrate the strong potential of crystallized PEDOT:PSS as a crucial component for a variety of versatile bioelectronic interfaces. Polymer electrodes: Crystallized films are suitable for cardiac interface Cardiomyocyte cells can be cultured and made to pulse on demand using transparent polymers with good stability. Conductive thin films formed from poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) have low impedances, making them ideal for bioelectronic interfaces. But they suffer from severe fragility in aqueous environments. Myung-Han Yoon from Korea’s Gwangju Institute of Science and Technology and colleagues have made PEDOT:PSS films that show no degradation up to three weeks underwater. They achieved this by immersing the films in concentrated sulfuric acid to initiate solvent-assisted crystallization. The crystalline films had improved electrical/electrochemical properties and biocompatibility over approaches such as polymer cross-linking, and supported photolithographic patterning into microelectrode arrays. Using cardiac cells as a model, the researchers demonstrated the feasibility of modulating beating frequencies with direct electrical stimulation under 1V while simultaneously capturing real-time act